/*
 * Copyright (C) 2014 Allwinner Ltd.
 *
 * Author:
 *	Ryan Chen <ryanchen@allwinnertech.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation, version 2 of the
 * License.
 *
 * File: fivm_crypto.c
 */

#include <linux/kernel.h>
#include <linux/file.h>
#include <linux/crypto.h>
#include <linux/scatterlist.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include "fivm.h"


static char *fivm_hash = "sha256";
static int init_desc(struct hash_desc *desc)
{
	int rc;

	desc->tfm = crypto_alloc_hash(fivm_hash, 0, CRYPTO_ALG_ASYNC);
	if (IS_ERR(desc->tfm)) {
		pr_info("FIVM: failed to load %s transform: %ld\n",
			fivm_hash, PTR_ERR(desc->tfm));
		rc = PTR_ERR(desc->tfm);
		return rc;
	}
	desc->flags = 0;
	rc = crypto_hash_init(desc);
	if (rc)
		crypto_free_hash(desc->tfm);
	return rc;
}
/*
 * Calculate the file hash(SHA256/SHA512) digest
 */
int fivm_calc_hash(struct file *file, char *digest)
{
	struct hash_desc desc;
	struct scatterlist sg[1];
	loff_t i_size, offset = 0;
	char *rbuf;
	int rc;

	rc = init_desc(&desc);
	if (rc != 0)
		return rc;

	rbuf = kzalloc(PAGE_SIZE, GFP_KERNEL);
	if (!rbuf) {
		rc = -ENOMEM;
		goto out;
	}
	i_size = i_size_read(file->f_dentry->d_inode);
	while (offset < i_size) {
		int rbuf_len;

		rbuf_len = kernel_read(file, offset, rbuf, PAGE_SIZE);
		if (rbuf_len < 0) {
			rc = rbuf_len;
			break;
		}
		if (rbuf_len == 0)
			break;
		offset += rbuf_len;
		sg_init_one(sg, rbuf, rbuf_len);

		rc = crypto_hash_update(&desc, sg, rbuf_len);
		if (rc)
			break;
	}
	kfree(rbuf);
	if (!rc)
		rc = crypto_hash_final(&desc, digest);
out:
	crypto_free_hash(desc.tfm);
	return rc;
}


